Appl Phys A (2008) 93: 655–661
DOI 10.1007/s00339-008-4691-z
Structure and impedance spectroscopy of Pr
1−x
Sr
x
Fe
0.8
Co
0.2
O
3−δ
(x = 0.1, 0.2, 0.3) thin films grown by laser ablation
I. Ruiz de Larramendi · R. López-Antón ·
J.I. Ruiz de Larramendi · T. Rojo
Received: 12 October 2007 / Accepted: 4 March 2008 / Published online: 27 June 2008
© Springer-Verlag 2008
Abstract Polycrystalline samples of Pr
1−x
Sr
x
Fe
0.8
Co
0.2
O
3−δ
(x = 0.1, 0.2, 0.3) (PSFC) were prepared by the
combustion synthesis route at 1200°C. The structure of
the polycrystalline powders was analysed with X-ray pow-
der diffraction data. The X-ray diffraction (XRD) pat-
terns were indexed as the orthoferrite similar to that of
PrFeO
3
having a single-phase orthorhombic perovskite
structure (Pbnm). Pr
1−x
Sr
x
Fe
0.8
Co
0.2
O
3−δ
(x = 0.1, 0.2,
0.3) films have been deposited on yttria-stabilized zirco-
nia (YSZ) single-crystal substrates at 700°C by pulsed
laser deposition (PLD) for application to thin film solid
oxide fuel cell cathodes. The structure of the films was
analysed by XRD, scanning electron microscopy (SEM)
and atomic force microscopy (AFM). All films are poly-
crystalline with a marked texture and present pyramidal
grains in the surface with different size distributions. Elec-
trochemical impedance spectroscopy (EIS) measurements
of PSFC/YSZ single crystal/PSFC test cells were conducted.
The Pr
0.7
Sr
0.3
Fe
0.8
Co
0.2
O
3−δ
film at 850°C presents a lower
area specific resistance (ASR) value, 1.65 cm
2
, followed
by the Pr
0.8
Sr
0.2
Fe
0.8
Co
0.2
O
3−δ
(2.29 cm
2
at 850°C) and
the Pr
0.9
Sr
0.1
Fe
0.8
Co
0.2
O
3−δ
films (5.45 cm
2
at 850°C).
I. Ruiz de Larramendi · J.I. Ruiz de Larramendi · T. Rojo ( )
Departamento de Química Inorgánica, Facultad de Ciencia
y Tecnología, Universidad del País Vasco, Apdo. 644,
48080 Bilbao, Spain
e-mail: teo.rojo@ehu.es
R. López-Antón
Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad
de Zaragoza, C/Pedro Cerbuna 12, 50009 Zaragoza, Spain
R. López-Antón
ISIS Neutron and Muon Facility, Rutherford Appleton
Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
PACS 72.60.+g · 61.05.cp · 68.37.Hk · 68.37.Ps
1 Introduction
Perovskite oxides, Ln
1−x
A
x
MO
3−δ
(Ln = rare earth;
A = Sr, Ca, Ba; M = Cr, Mn, Fe, Co, Ni), exhibit a va-
riety of magnetic and electronic properties. For example,
some perovskites display good performance as cathode ma-
terials in high temperature solid oxide fuel cells (SOFCs),
because of their mixed electronic and ionic conductivity.
La
1−x
Sr
x
MnO
3
(LSM) perovskites are representative elec-
tronic conductors that have been extensively used as cath-
odes in ZrO
2
-based SOFCs [1]. These are good electronic
conductors, but the lack of oxide-ion vacancies and its con-
ductivity at the working temperatures make it necessary
to use thick and porous electrodes containing an array of
triple-phase boundaries where gas, electrolyte and electrode
meet. These LSM oxides have the disadvantage of forming
the low oxide ion conductivity product of the pyrochlore
oxide La
2
Zr
2
O
7
at the boundary with the electrolyte and
yttria-stabilized zirconia (YSZ) under an annealing tem-
perature of more than 1200°C, restricting the fabrication
processes of SOFCs. Since the reactivity depends on the lan-
thanide element and the Sr content, it is an option to employ
Pr
0.7
Sr
0.3
MnO
3
cathodes, which exhibit better compatibil-
ity with YSZ [2].
In recent years, the employment of lanthanum cobaltites
has been investigated as cathodes [3]. Initially, the investi-
gations were centred on the La
1−x
Sr
x
CoO
3−δ
(LSC) com-
pound due to its considerable ionic conductivity and suf-
ficient electronic conductivity, turning LSC materials into
an interesting mixed ionic–electronic conductor (MIEC) [4].
The disadvantage that presents this series of compounds is
its reactivity with the YSZ electrolyte; hence they must be